Synthesis And Magnetic Properties Of Single Molecule Magnets Based On O-vanillin Schiff Base Ligands

The thesis mainly focused on the synthesis,structures and properties of coordination complexes supported by nitrogen-containing ligands.Twenty-one coordination complexes were synthesized by solvothermal reaction.The magnetic properties of several complexes were investigated.These results were described as follows.Eightisostructuraldinuclearlanthanidecomplexesoftheformula[Ln₂L₂¹（NO₃）₂（C₂H₅OH）₂]?0.5py（Ln=Eu（1）,Gd（2）,Tb（3）,Dy（4）,Ho（5）,Er（6）,Yb（7）,Y（8））have been hydrothermally synthesized by employing a relatively rigid and bulky Schiff base 2-{[（2-hydroxy-3-methoxybenzyl）imino]methyl}naphthalen-1-ol（H₂L¹）as a ligand.The structures of the isomorphous complexes 1-8 were determined by IR,X-ray crystallography and X-ray power diffraction.The direct current magnetic susceptibility data of 2-6 were collected in the temperature range of 300-2 K.Complexes[Dy₂L₂¹（NO₃）₂（C₂H₅OH）₂]?0.5py（4）and[Ho₂L₂¹（NO₃）₂（C₂H₅OH）₂]?0.5py（5）display slow magnetic relaxation behavior.It is worth mentioning that the U_eff for 4 of 66.7 K is a relatively high value among the reported Dy₂ SMMs.This work demonstrates the potential applications of the H₂L¹ ligand in the synthesis of SMMs.Eight isostructural mononuclear transition metal complexes[M（DH₂PIP）Cl₂]（M=Cu（9）,Ni（10）,Mn（11）,Fe（12））,[Cu（DH₂PIP）Br₂]（13）,and[M（DBr₂PIP）Cl₂]（M=Cu（14）,Ni（15）,Mn（16））,supported by two nitrogen-containing heterocyclic ligands2,6-bis（imidazo[1,5-a]pyridin-3-yl）pyridine DH₂PIP（H₂L²）and 2,6-bis（1-bromoimidazo[1,5-a]pyridin-3-yl）pyridine DBr₂PIP（L²）,were synthesized and characterized.The structures of the isomorphous complexes 9-16 were determined by IR,X-ray crystallography and X-ray power diffraction.Because of the potential applications of dichloro coordination compounds as catalysts for olefin polymerization,the catalytic properties of these complexes will be further studied.Two isostructural dinuclear transition metal complexes[Cu₂（L³）₂]（17）and[Ni₂（L³）₂]（18）werehydrothermallyaffordedbyemployingSchiffbase4-（（1-hydroxy-2,3-dihydro-1H-inden-2-yl）amino）pent-3-en-2-one（H₂L³）as a ligand.The structures of the isomorphous complexes 17 and 18 were determined by IR,X-ray crystallography and X-ray power diffraction.The direct current magnetic susceptibility data of 17 and 18 were collected in the temperature range of 300-2 K.Ferromagnetic interactions are found for complex 17.Three isostructural Ni₄Ln₂ complexes of formula[Ni₄Ln₂L₄¹（NO₃）₂（OH）₄（C₂H₅OH）₂]（Ln=Nd（19）,Ho（20）,Yb（21））have been hydrothermally synthesized by employing Schiff base 2-{[（2-hydroxy-3-methoxybenzyl）imino]methyl}naphthalen-1-ol（H₂L¹）as the ligand.X-ray crystallography analyses revealed that the metal ions of the complexes are bridged by hydroxyl groups to form defective dicuban-like structures.